First 2020 West Nile Virus Case Confirmed In San Mateo County

SAN MATEO COUNTY, CA — The first known case of West Nile virus in San Mateo County of this year was detected earlier this week, the San Mateo County's Mosquito and Vector Control District said Wednesday in a news release.

The county’s first WNV case since 2018 was detected in a dead bird -- an American crow – found in South San Francisco.

Though reports of dead birds indicate presence of the virus, the risk to humans remains low.

West Nile virus primarily affects birds, but humans, horses and other animals can get infected if bitten by an infected mosquito, which are vectors for the virus.

The virus cannot be spread person to person. The county's vector control district encouraged people to report fresh bird carcasses to the California West Nile Virus Hotline at www.westnile.ca.gov or by calling (877) WNV-BIRD.

People can reduce the risk of infection by preventing mosquito breeding and avoiding mosquito bites.

Since mosquitoes lay their eggs on standing water, the district recommends draining and eliminating sources of standing water on properties -- including flower pots, old car tires, clogged gutters and pet bowls.

People should also wear clothing and mosquito repellent if outside during early morning and evening hours, as these are times the mosquitoes that transmit the virus tend to bite.

Doors and windows should have tight-fitting screens to keep mosquitoes out. Mosquito repellent containing ingredients such as DEET, picaradin, oil of lemon eucalyptus, or IR3535 can prevent mosquito bites.

The district will continue to treat mosquito breeding sources and collect mosquitoes for testing in areas where dead birds are found.

“In addition to ongoing surveillance for West Nile virus, the District continues to control mosquitoes in their immature stages through an integrated pest management (IPM) program,” the SMCMVCD said.

“The District’s vector control technicians routinely inspect standing water where mosquitoes develop, and treat mosquito breeding sources throughout the county.”

For assistance with a mosquito problem, people can contact the district at (650) 344-8592 or visit www.smcmvcd.org for more information.

West Nile virus has also been found in Contra Costa and Santa Clara counties this year.

— Bay City News and Patch Editor Gideon Rubin contributed to this report